the type defined for the container

The STL defines the following types for all containers :

container:: value_type , such as vector<int>::value_type for int type

(Note: For ordinary, it is its type, for map, it is pair<int, string> type )

container:: reference , such as list<int>::reference for int &

container:: const_reference , such as set<int>::const_reference means const int &

container:: iterator , such as list<int>::iterator means iterator to int

container:: const_iterator , const iterator

Container:: different_type , which represents the distance between two iterators, similar to the difference between pointers.

Container:: size_type , an unsigned integer representing the number of elements of the container object.

The types defined by the STL specifically for associative containers are:

Container:: key_type , indicating the type of the keyword, such as map<int, string>::key_type=int

container:: mapped_type , the type of the value in the map/multimap, string in the above example

container:: key_compare , the object class of the keyword comparison function, defaults to less<Tkey>

Container:: value_compare , for set/multiset, same as key_compare; for map/multimap, provides sorting function for value_type

        #include<iostream> 
      

        #include<map> 
      

        using namespace std; 
      

        template<class container> 
      

        void print_container(container& v) 
      

{

                for(auto& elem:v) 
      

                        cout<<elem.first<<","<<elem.second<<endl; 
      

}

        intmain() 
      

{

              
       //STL defines types for all containers

 
       //The value_type here is equivalent to pair<int,string>

                
       map<int,string>::value_type
        arr[4] =

{

                        
       map<int,string>::value_type
       (1,"kunming"),

                        map<int,string>::value_type(3,"nanning"), 
      

                        map<int,string>::value_type(2,"guiyang"), 
      

                        map<int,string>::value_type(3,"haikou") 
      

};

                map<int,string> map1(arr,arr+4); 
      

                print_container(map1); 
      

              
         map<int,string>::size_type size 
       = map1.size();

                cout<<"map1.size="<<size<<endl; 
      

                
        map<int,string>::key_type
        cnt = map1.erase(3);

                cout<<"map1 after erase key 3"<<endl; 
      

                print_container(map1); 
      

                cout<<"erase count="<<cnt<<endl; 
      

                cout<<"----华丽的分割线----"<<endl; 
      

                multimap<int,string> mmap1(arr,arr+4); 
      

                print_container(mmap1); 
      

multimap<int,string>::size_type msize = mmap1.size();

                cout<<"mmap1.size="<<msize<<endl; 
      

multimap<int,string>::key_type mcnt = mmap1.erase(3);

                cout<<"mmap1 after erase key 3"<<endl; 
      

                print_container(mmap1); 
      

                cout<<"erase count="<<mcnt<<endl; 
      

                return 0; 
      

}